In humans, the gene causing 1 of the forms of hereditary deaf-mute is recessive in relation to the gene of normal

In humans, the gene causing 1 of the forms of hereditary deaf-mute is recessive in relation to the gene of normal hearing from the marriage of a deaf-mute woman with a normal man, a deaf-mute child was born, determine the genotypes of the parents.

Recessive gene – a, Dominant gene – A.
We know that a woman is deaf and dumb, this is possible only with aa. We also know that the child is deaf and dumb, that is, it has the same genotype as that of the mother. Hence the man’s father is Aa.
thus for the mother – aa, for the man – Aa.